An example of a conventional air-conditioning apparatus such as a multi-air-conditioning apparatus for buildings is an air-conditioning apparatus that causes a refrigerant to circulate from an outdoor unit to a heat medium relay unit (relay unit) and that causes a heat medium such as water to circulate from the heat medium relay unit to indoor units, so as to reduce the power used to convey the heat medium while causing the heat medium to circulate to the indoor units (for example, Patent Literature 1).
Further, an example of a conventional air-conditioning apparatus that uses a non-azeotropic refrigerant mixture is a chiller air-conditioning apparatus that causes a non-azeotropic refrigerant mixture and a heat medium to flow through a heat exchanger related to heat medium (refrigerant/heat medium heat exchanger) in opposing directions (that is, the flows are in counter flow) to improve heat exchange efficiency (for example, Patent Literature 2).
Further, an example of a conventional air-conditioning apparatus that uses a non-azeotropic refrigerant mixture is a chiller air-conditioning apparatus that causes a non-azeotropic refrigerant mixture and a heat medium to flow through a heat exchanger related to heat medium serving as an evaporator of a refrigerant circuit in parallel in the same direction (that is, the flows are in parallel flow) to prevent freezing of the heat medium while keeping the temperature of the heat medium at the inlet of the heat exchanger related to heat medium constant (for example, Patent Literature 3).
Further, an example of a conventional air-conditioning apparatus that uses a non-azeotropic refrigerant mixture is an air-conditioning apparatus of a heat pump based cold/hot water pumping type configured such that a four-way valve is switched to reverse a refrigerant flow passage of a heat exchanger related to heat medium so that a refrigerant and a heat medium are in parallel flow in the heat exchanger related to heat medium during a cooling operation and a refrigerant and a heat medium are in counter flow in the heat exchanger related to heat medium during a heating operation (for example, Patent Literature 4).